fix: removed equality method from Literal class

[kevinclancy]

Notes

Slither's Literal class implements an __eq__ method but not a __hash__ method, making it unhashable. The eq implementation was introduced in this PR so that two distinct occurrences of int[n] are treated as equal types, where n is some literal integer; that was a flawed solution, because it doesn't take into account cases where constants and arithmetic expressions occur in the type expression, e.g. int[CONST_1 + CONST_2]

Another problem with giving Literal a custom equality operator is that all other Expression subclasses use the built-in equality implementation, which is reference equality. It is confusing to have different Expression subclasses using different notions of equality.

This PR makes Literal hashable by moving the literal equality hack from the Literal class into the ArrayType class.

Testing

• Copy this under utilities/slither in a local copy of the slither-task repo.
• Run make test and verify that all tests succeed
• Run ./evaluate.sh run 100 and verify that all projects succeed
• Print the IR for the code from this issue and verify that a LIBRARY_CALL operation is generated.

Related Issue

https://github.com/CertiKProject/slither-task/issues/674

Additional Comments

I created an issue about how giving Literal an equality method didn't fix the issue it intended to solve:
https://github.com/CertiKProject/slither-task/issues/689
This issue remains unresolved.

[duckki]

Have a question. Otherwise, it makes sense.

[duckki]

looks good.

[duckki]

I confirmed https://github.com/CertiKProject/slither-task/pull/663 is no longer crashing.